1. Field of the Invention
This invention relates to a production method for a mold for the continuous casting of low carbon steel, high carbon steel, stainless steel and special alloy steel, and, furthermore, relates to a production method for a mold for continuous casting having a water cooling mechanism.
2. Description of the Prior Art
A mold for continuous casting, which is made of copper or a copper alloy, generally has good heat conduction properties and is equipped with a water cooling mechanism because ingot steel injected into the mold has a high temperature. With regard to molds for continuous casting having conventional water cooling mechanisms, there are the slit type, canal type and stud bolt type, named by the shape of the cooled water path on the reverse surface of the cast. Regarding the stud bolt type, the cast does not have a cooled water path, but is connected to the cooling water path by bolts. The slit type is more commonly used. FIG. 4 (a), (b) are exploded perspective views of the slit type water cooling cast. 1 is a back frame (a water case) comprising of iron or stainless material. The back frame 1 is divided into upper and lower half parts, the upper half part is connected to the cooled water inlet 2 and the lower half part is connected to the cooled water outlet 3. On the surface opposite to the back frame 1, the slits 5 are provided in a vertical orientation. The cooled water flows into the slits 5 from the lower half part of the back frame 1 through the water supplying channel 6 and flows out to the upper half part of the back frame 1 through the draining channel. The cast 4 is fixed to the back frame 1 by bolts 8. For this reason, penetration holes are required for the bolts 8 and a packing 9 is provided to prevent the leakage of water out of the back frame 1. An O-ring 11 is also required to prevent the leakage of water between the back frame 1 and the cast 4. Furthermore, installment holes 10 are required for the bolts 8. Accordingly, it is not possible to make slits in the place where the installment holes are made, and it is not always possible to make the slits of the cast at equally spaced intervals. This results in the cooling not being uniform.
FIG. 5 (a), (b) are exploded perspective views of the canal type water cooling mold. The difference between the canal and slit type is that, in the canal type, the cooling water path made in the mold 4 is not provided on the surface of the mold, but penetrates the interior of the mold. Accordingly, with regard to the canal type, the thickness of the plate of the mold tends to be greater than that in case of the slit type. The mold 4 and the back frame 1 are attached by bolts 8. Accordingly, it is required to provide both the mold 4 and the back frame 1 with bolt holes and to provide packings to prevent the leakage of water. It is also required to arrange the installment holes of the bolts 8 between the cooled water paths in the cast 4. Therefore, the pitch of the cooled water path cannot be as narrow as desired. This causes the cooling capability to lower.
FIG. 6 is an exploded perspective view of the stud bolt type water cooling mold. The difference between the stud bolt type and the former two cases is that its cooled water paths are not made on the side of the mold 4. In the stud bolt type, the cooled water paths are formed as slits on the surface of the back frame 1 opposite to the mold, the cooled water flows from the cooled water inlet 2, along the surface of the back frame 1 and the mold 4, and out of the cooled water outlet 3. On the surface of the mold 4, opposite the back frame 1, stud bolt holes 2 are provided and the bolts are inserted therein. The bolts 8 are inserted into the bolt holes 2, and fixed by the nuts 3 and packings 9. Furthermore, it is necessary to have an O-ring between the back frame 1 and the mold 4 to prevent the leakage of water.
In the above-mentioned conventional techniques, the water cooling mechanism and the mold are made separately and physically united prior to use. Accordingly, there have been the following problems in the use of the bolt type water cooling mold.
(a) Packings and an O-ring are required to prevent the leakage of water when the water cooling mechanism and the mold are united, and, when fatigued, the leakage of water may be increased.
(b) Installment holes and bolts are required on the reverse surface of the mold in order to unite the water cooling mechanism and the mold, therefore, a thicker copper or copper alloy material is required for the mold than which is originally needed, and further, the cooled water path cannot be located in the places where the installment holes etc. are set. Accordingly, the cooling is not uniform.
(c) Furthermore, since a thick copper or copper alloy material must be used, the cooled water path must be positioned in the interior or on the reverse surface of the mold by several methods. When the stud bolts are installed on the reverse surface of the mold, although the cooled water path is not placed in the mold in order to avoid the reduction of the plate thickness of the mold, the stud bolt processing takes a much longer time than the installation of the installment holes.
(d) To assemble the mold and the water cooling mechanism, processing is not only required on the side of the mold, but is also required to install the mold on the side of the water cooling mechanism.